Simplify bar when coverage is zero.
Simplify bar when coverage is zero.

When coverage is zero, the bar is black because of the border.  In
this case, it makes more sense to remove the bar altogether.

thatguystone/gcovr,cloudsmith-io/gcovr,cloudsmith-io/gcovr,kevincon/gcovr,cloudsmith-io/gcovr,thatguystone/gcovr,kevincon/gcovr,kevincon/gcovr,thatguystone/gcovr,cloudsmith-io/gcovr,kevincon/gcovr,thatguystone/gcovr